1. Field of the Invention
The present invention relates to oil-filled protectors for use with electric motors and, more particularly, for use with electric submergible motors to be suspended within wellbores.
2. Description of Related Art
Electric submergible pumps are widely used throughout the world for recovering subterranean fluids to the earth""s surface. For the long term successful operation of such submergible pumping systems, the electric motor must be supplied with uncontaminated cooling motor oil. This cooling oil is partially contained within one or more elastomeric bags within a motor protector. Unfortunately, in wellbore environments with elevated temperatures, such as greater than about 300 degrees F., conventional motor protector bags rapidly deteriorate and split so that the motor oil will become contaminated by wellbore fluids. This contamination can directly lead to shortened operational life, which in turn will cause the premature shutting-in of the well, and the costly removal and repair of the submergible pumping system.
Specifically, the elastomeric motor protector bags are generally cylindrical in shape and are sealed within an oil filled housing. The bags are filled with oil at the time of installation to an expanded state. With the rise of temperature caused by the immersion in the wellbore, as well as the thermal expansion caused by the operation of the electric motor, the bags tend to slightly expand even more. When the electric motor is turned off, the cooling oil cools and contracts. This contraction allows the motor protector bag to deflate. The repeated expanding and contraction of the elastomeric bag can cause splitting or cracks in the bag under certain conditions.
The elastomer typically used for the elastomeric bags is a saturated nitrile. This material exhibits a satisfactory combination of elasticity and tear resistance at operating temperatures up to about 300 degrees F. However, above about 300 degrees F., the saturated nitrile becomes brittle and looses its elastomeric properties. Other materials can be used to produce an elastomeric bag with satisfactory elasticity up to about 400 degrees F., such as fluorine containing co- and ter-polymers and ethylene propylene diene methylene-based terpolymers. These materials, however, do not have the needed tear resistance at the temperatures above about 300 degrees F. to withstand the repeated expansion and contraction.
There is a need for an improved elastomeric bag for use within an oil-filled electric motor protector that exhibits satisfactory elasticity and tear resistance in a wellbore environment and at temperatures above about 300 degrees F.
The present invention has been contemplated to overcome the foregoing deficiencies and meet the above described needs. Specifically, the present invention is a reinforced elastomteric bag for use within an oil-filled electric motor protector with the bag body formed from elastomeric material selected from the group consisting essentially of: tetrafluoroethylene-propylene copolymer, vinylidene fluoride hexafluoropropylene copolymer, virtually saturated acrylonitrile-butadiene copolymer, vinylidene fluoride-perfluoromethylvinylether-tetrafluoroethylene terpolymer, vinylidene fluoride hexafluoropropylene tetrafluoroethylene terpolymer, ethylene propylene diene methylene-based polymers, and combinations thereof; and a reinforcing material selected from the group consisting essentially of: tetrafluroethylene, aromatic p-polyamides, aromatic o,m-polyamides, fiberglass, ferrous metal, nonferrous metal, and combinations thereof. The reinforcing material is in the form of particles, threads and/or a weave that is dispersed within, bonded to or layered within the elastomeric material in a manner to improve the tear resistance of the bag at elevated temperatures.